Typhoid fever is perceived to be a major problem in India, but its true incidence is uncertain. In preparation for future field trials of typhoid vaccines, this research established an urban field site in New Delhi, India, to monitor typhoid incidence in a cohort of subjects. The site in Delhi comprised a population of about 19,000 persons. During 12 months of surveillance, the incidence of typhoid fever was 9.9 cases per 1,000. All cases of typhoid were followed for up to 3 months to determine typhoid-related disability, and case-control studies were nested within these cohorts to assess foods, water sources, and hygienic practices associated with typhoid risk, as well as the role of H. pylori coinfection in influencing this risk.Project will be terminated in 1999. - Salmonella typhi, typhoid fever, India, surveillance, incidence - Human Subjects